Pump controlling mechanism



April 20, 1943. H. E. ADAMS 2,317,091

PUMP CONTROLLING MECHANISM Filed Aug. 2, 1940 3 Sheets-Sheet l In mm forHfl/FDZD 190,013,

fltornegs April 20, 1943. v ADAMS 2,317,091

PUMP CONTROLLING MECHANISM Filed Aug. 2, 1940 a Sheets-Sheet 2 H Inz/entor #19901 D E/YDflM-S fliiorneys April 20, 1943, MS 2,317,091

PUMP CQNTROLLING MECHANISM Filed 2, 1940 s Sheets-Sheet 3 V I w w R 1 Il 4 & ,r H

Inventor M /P010 fl0/7M6,

flttorncy Patented Apr. -20, 1943 PUMP CONTROLLING MECHANISM Harold E.Adams, South Nor-walk, Conn., assignor to Nash Engineering Company,South Norwalk, Conn., a corporation of Connecticut Application August 2,1940, Serial No. 349,956 7 Claims. (Cl. 103-97) This invention relatesto liquid pumping systems and more particularly to a new and improvedmechanism for controlling the operation of a centrifugal or other typeof liquid pump.

It is well known that a centrifugal pump becomes less eilicient inoperation even to the extent of a complete breakdown of its normaloperating characteristics, if air or gas becomes entrained in the liquidflow through the pump, or if the pump becomes air bound, and accordinglyit is a primary object to prevent uncovering of the eye of thecentrifugal impeller, the suction connections, or the inlet to the pumpwhere such uncovering would be objectionable, and thereby prevent inletof such air or gas to the pump, and hence to the pump discharge.

The efilcient operation'of pumps of this nature requires maintenance ofa reasonable pressure in the volute of the pump and it is a furtherobject to so control the discharge of the pump as to maintain thenecessary pressures within the pump.

It is important in systems utilizing pumps of this nature that theliquid discharge from the pump be controlled, that is, cut oil at timeswhen otherwisethere might be insufficient liquid supplied to the pump,not only in order to maintain efficient operation, but to prevent flowof air or gas through the liquid discharge connections with resultantdeleterious effects to apparatus beyond the pump discharge. As anexample of such deleterious results, if the pump discharges to a pipeline, and air is carried along with the liquid,

. this tends to cause corrosion in the pipe. Again,

if the pump is applied to a heating system, as in the case of returningcondensate from the returns of a heating system to the boiler, and airis discharged from the pump it will tend not only to corrode the boilershell and tubes, but also it will put air into a system where steam isto be used.

While the present invention is of general application, and by no meanslimited to use in a heating system, for purpose of illustration atypical arrangement is herein illustrated which might be readily adaptedto use with a vacuum steam heating system, or in any type of a system inwhich a receiver from which liquid is to be pumped, and discharged backinto the system, is utilized.

Specifically it is a feature of the invention to obtain the desiredoperating results by the use of a valve in the discharge of thecentrifugal pump, which is controlled by a pilot valve between thedischarge valve and the receiver, whereby the discharge from the pumpcan be controlled by conditions in advance of the pump.

A further object of the invention isto provide a discharge control whichallows the centrifugal pump to discharge liquid at its full normalcapacity, or to throttle the discharge of the pump to the rate of inflowinto the receiver or to the pump, or to entirely cut oil the discharge,should the inflow to the pump cease.

To the attainment of the foregoing and other objects which will appearas the description proceeds, reference may be made to the accompanyingdrawings, wherein:

Fig. 1 is an elevation partly in section, diagrammatically showing atypical arrangement of a centrifugal pump and receiver with the controldevices;

Fig.2 is a vertical section of one form of piston operated dischargevalve;

Fig. 3 is a vertical section partly in elevation of a pilot controlvalve for the discharge valve, showing a float mechanism for actuatingthe pilot valve;

Fig. 4 is a vertical section illustrating a variation of a dischargevalve, difiering from that in Fig. 2 by the employment of a diaphragm inlieu of the piston, as a controlling means for the valve;

Fig. 5 is a vertical section illustrating a further modification,utilizing a bellows arrangement, functioning similarly to the action ofthe piston or diaphragm of Figures 2 and 4;

Fig. 6 is a vertical section showing a different type'of dischargevalve, operable by any of the forms of actuator shown in Figures 2, 4 or5; and

Fig. 7 is an elevation partly in section, diagrammatically showing atypical arrangement of a centrifugal pump and receiver with a variationin the control devices from that disclosed in Fi 1.

Referring now to the drawings wherein like reference numerals designatelike parts and particularly with reference to Fig. 1, it will be notedthat the apparatus of the present invention comprises generally areceiver ill, a centrifugal pump H having its inlet or suctionconnection l2 connected to the receiver l0 and a discharge line ii. Adischarge valve assembly I 4 is interposed between the line I3 and amain discharge pipe I! leading to any suitable point to which it isdesired to pump liquid from the receiver. If this apparatus isinterposed in a vacuum steam heating system, the main pipe line I! willrun to the supply side of the system and the returns from the systemwould be connected to the receiver through the receiver inlet IS.

The centrifugal pump may be driven in any conventional manner by a primemover M which may be a pulley drive, an electric motor, or any desirableequivalent. A pilot valve assembly indicated generally at IT, isconnected by a control pipe line l3 to the lower portion of the assemblyH, the pilot valve being controlled by a float i9 having a float rod 20within the receiver l0.

With this set up, and the centrifugal pump in operation, liquid will bedrawn from the receiver l3 through the suction connection or inlet l2 tothe eye 2| of the impeller 22, and by centrifugal action into the volute23 and thence into the pump discharge line i3. The main body of flowthrough the valve assembly I will of course be from the line l3 to themain discharge pipe I6, the flow rate being controlled by the postion ofthe movable valve 26.

Referring now particularly to Fig. 2, it will be seen that the valve 26is provided with a depend-.

ing skirt 2! ported'or cut away as indicated at 23. The valve stem 23terminates at its lower end in a piston 33 operable in a guide cylinder3|, there being tolerable clearance provided between the piston and itsguide cylinder for a purpose which will appear. The valve proper 26cooperates with a valve seat 32, the diameter of which is less than thediameter of the piston 30. When the valve assembly is in its full downward position with the valve 26 engaging its: seat 32, it completelycloses the connection between the pump discharge line 13 and the maindischarge linet l5, by forming a tight seat at 32. As the valve opens,it provides a graduated increase in flow from line [3 to line l5, inproportion to the lift of the valve, due to the gradual uncovering ofthe ports 28 in the valve skirt 21.

The valve of course is guided by the skirt and the piston 30 operatingin the guide cylinder 3|.

The closing and opening of the valve assembly is produced by thehydraulic balance, or unbalance, maintained by the action of acontrolling pressure on the bottom or underside of the piston 33,through the operation of the pilotvalve 33 in the assembly I1, and thepressure difference generated by the centrifugal pump itself.

As stated, there is a reasonable or tolerable clearance between thepiston 30 and the walls of the piston guide cylinder 3|, and it has alsobeen pointed out that the diameter of the piston is greater than thediameter of the valve seat 32. Coming back'to the pilot valve assemblyH, the valve proper 33 is normally held closed on its seat 34 by meansof a light spring 35, and the normal differential in pressure, createdby the centrifugal pump, between the control line I8 and the interior ofthe receiver l3. Provision is made for opening the pilot valve 33 by theweight of the float i3 and its rod or stem 23, when operating about afulcrum 36. The end of the rod 20 is slightly extended to engage anextension or stem 31 on the valve 33 when the float 19 drops due to alowering of the normal level of liquid within the receiver. I

It is desired to maintain the level of liquid in the receiver above theopening to the suction or inlet l2 of the pump, and thus constantlymaintain the eye of the pump submerged or below the level of liquid inthe receiver, and accordingly the float assembly is positioned such thatit is inoperative to open the valve 33 unless and until the level ofliquid in the receiver drops below a predetermined level or pointindicated generally at 33, In other words, the weight of the float I3 isonly operative to open the valve 33 when the liquid level in thereceiver reaches the desired low limiting point 33, and at any higherlevel, the natural buoyancy of the float removes pressure from the valvestem 31 and the valve is thus maintained in a normally closed position.

Under normal operating conditions, when the centrifugal pump is running,a pressure is maintained in the pump discharge line l3 that is of coursegreater than the pressure in the suction connection or inlet l2 to thepump, and hence greater than the pressure within the receiver l3.Assuming the pilot valve 33 to be in its normal closed position, withthe liquid level in the receiver at or above the arbitrary level 33,there can be no flow in either direction through the control line l3,and consequently the pressure on the bottom or underside of the piston33 of the discharge valve 26, will be equalized with that on the top orupper side, by the natural transmission of liquid pressure through theclearances provided between the piston and the guide cylinder 3|. Alsoit is obvious that the pressure on the pump discharge line l3 will behigher than the pressure in the main discharge conduit II when thecentrifugal pump is in operation.

Because of this higher pressure on the underside of the valve 26 fromthe line I3, this pressure diiference will cause the valve 26 to liftand allow a flow to the main dischargeline ii, the amount of flow andthe degree of lift depending upon the pressure drop that exists acrossthe valve. Whenever the centrifugal pump is shut down, the pressure inthe discharge pipe [3 will immediately drop and go below that existingin the main line IS. The immediate resultant tendency to reversal offlow will cause a closing of the valve 26, seating same tightly on theseal 32. In thisrespect, the action of the valve 26 is quite similar tothat of a conventional check valve, except that this action is cushionedand thus improved by the snubbing action of the piston 30 operating inits guide cylinder I. Should the pump continue to operate, and

reduce the liquid level in the receiver l3 to a" point-below the level33, the float 13, in lowering, will open the pilot valve 33. A flow willimmediately start, with the opening of the pilot valve, through theclearance between the piston 33 and its guide cylinder 3|, into theunderside of the chamber formed by the guide cylinder below the piston,and thence back through the control line l3 and the valve 33 into thereceiver Ill. The size of the opening through the valve seat 33, andpast the stem 31 is proportioned suflicientiy great so that when thevalve is fully opened by the flow, liquid leaking through the clearancespace between the piston 30 and the cylinder walls 3| will flow freelyinto the receiver I! with a minimum of restriction. In fact. the onlyrestriction of such flow is around the piston 33, within the guidecylinder.

Opening of the valve 33, therefore, provides for the reduction inpressure beneath the piston 30. This reduction in pressure on theunderside ofthe piston causes an unbalance in pressure between theunderside of the piston, and the top 'or upper side thereof where thefull discharge pressure of the centrifugal pump is being applied to thepiston through the line l3. This diflerence in pressure produces adownward movement of the valve 26, tending to throttle or close oil. theflow from line l3 to the main discharge line [5.

If the pilot valve 33 is opened wide by the rapid falling of the liquidlevel in the receiver l it will immediately create a large unbalance ofpressure across the piston 39, and because of the greater diameter ofthe piston with respect to the diameter of the valve seat 32, it willovercome the upward pressure exerted by the flow through the dischargeline i3 on the valve 26, and will thus firmly close the valve on theseat 32.

In addition to the difference in area between the valve 26 and thepiston 30, there is the additional pressure in the top of the valveassembly, exerted from the main discharge line l5, and also theapplication of pressure by a seating spring 39, positioned between thetop of the valve 26 and the underside of the top wall of the housing ofthe assembly [4, all of which further tends to maintain the valve tighton its seat 32. With this arrangement, it will be evident that further'pumping of liquid from the receiver to is stopped before the liquid inthe receiver can drop materially below the minimum desired level 38,which level is established at an appropriate point effective to preventa reduction of liquid level to a point where air might be drawn into thesuction connection or inlet of the centrifugal pump, thus effecting theadvantages and eliminating the objections heretofore mentioned.

Should liquid continue to flow into the receiver in through its inletl6, at a rate lower than the normal discharge rate of the centrifugalpump, then the arrangements described herein provide for throttling ofthe discharge from the centrifugal pump by the valve 26, so as tomaintain the same rate of discharge past this valve as the incoming rateof flow through the inlet Hi. This is caused by the throttling effectfrom the float control valve 33, and liquid level in the receiver I0,when the throttling action of the valve 33 stops free flow of liquidaround the clearance spaces between the piston 30 and the cylinder 3|,to an extent where suflicient pressure will be built up on the undersideof the piston 30 to balance the other pressure forces in the pipe linesl3 and [5, to a point'where a balanced condition is reached, by thethrottling action of the ports 28 in the valve skirt 21.

The pressure variation between the normal operating point and theshut-oil or closed discharge point of a conventional centrifugal pump isnot a wide enough variationto cause any difliculties such as building updetrimental pressures within the pump. The equalization of the pressureon the under side of the piston 30, with the pressure forces in thelines l3 and I5 prevents the building up of unfavorable pressures in thepump even should the discharge characteristic of the centrifugal pumpcover a wider than nonnal range of pressures.

It is contemplated that other types of liquid pump than the purecentrifugal type may be used in a system such as that herein described,and that the discharge control mechanism will be equally applicable. Insome instances, however, particularly if an impact or scraper type ofliquid impeller is utilized, it is within the scope of the invention touse a pilot control valve which would operate the main cut-off valve inthe discharge, as a by-pass valve rather than as a shutoff valve,because of the different characteristics of the pump. An impact orscraper type of pump requires increased power and almost unlimitedpressure build-up when the discharge is used in exactly the same manneras described heretofore, but instead of closing the discharge, the mainvalve would open a by-pass which would carry the discharged liquid backto the receiver or suction side of the pump, and the liquid would merelyrecirculate during the period of time that the pilot valve is opened.This would, therefore, require a main valve similar to the valveorganization H, but reverse acting. The by-pass line would merely be apipe line extending from the discharge to the receiver, substantiallyparalleling the control line [8, with an appropriate pressure checkvalve from the pump chamber.

As a variation in structure of the piston type discharge valve,reference may be made to Figure 4 wherein the piston is eliminated infavor of a pressure diaphragm 49, and orifices H-IZ are provided toestablish communication between the chambers below and above thediaphragm 49, in lieu of the clearance between the piston 39 and theguide cylinder 3i. It is obvious that the operation of this form ofstructure is identical with that described in Fig. 2.

As a slight modification of the flat diaphragm idea, a bellows diaphragmis illustrated in Fig. 5. This form of control utilizes the bellows dieframe 43 but is in all other respects the same as to operation as theforms illustrated in Figures 2 and 4. The eifective area of either thediaphragm or bellows, is of course, greater than that of the valve 26.

Fig. 6 shows a modification in the valve head portion of the structure,and since any of the control means, i. e., piston, diaphragm or bellowsmay be utilized, no description thereof is necessary. In this form ofdischarge valve, the valve head varies from those of Figures 2, 4 and 5in that it is made in two parts, one a floating valve member 44 whichseats directly on the main valve seat 32, and the other a sphericalseated, auxiliary valve member 45 attached to the valve stem 29,

which is in turn guided by the control means (not shown) at the base ofthe stem, and a guide piston 46 operating in the head of the assemblyl4.

The floating valve member 44 is guided by a relatively loose fit withthe stem 29, and as stated, the stem 29 with the auxiliary member isguided in part by the guide element 46 operating in the head of theassemblage l4. Because of the spherical seating arrangement, the member45 automatically takes its seat at 41, when the valve closes, to form atight seal with the floating member 44.

In action, the floating member 44, upon the stopping of the pump,immediately drops in position on the valve seat 32, thus stopping backflow from the pipe line IS. The valve member 45, under the action of thediiferential pressure across it, follows up this closing action moreslowly to finally seal oil minor leakage around the guiding surface ofthe floating member 44, and forms a leakproof seat with theself-aligning spherical arrangement 31.

The floating member 44, of course, previous to this, has adapted itselfto its seat on the valve at 32. The two seats are thus bothself-aligning and leak proof after the final closing action, and thecombination of the two provides a selfaligning valve, and has thefurther advantage of quick closing upon stoppage of the centrifugal pumpregardless of any sluggish action which might follow when the valve stemis controlled by a bellows, diaphragm, or piston.

While the form of invention embodied in Fig. l is preferable because ofits simplicity and mechanical action, it may be desirable to control"the pilot electrically, and Fig. 7 is illustrative of one mode of socontrolling the apparatus. In this form of the invention, instead of amechanical pilot valve arrangement, operable directly by the float inthe receiver, a float controlled electric snap switch 48 operating anormally been closed. The control line i8 can be tapped into thereceiver at any suitable point below the minimum liquid level, asindicated at 54. Except for the electric actuation of the pilot valve 49the operation of this form of apparatus is exactly the same as thatdescribed in connection with Fig. 1.

The advantages and operation of the invention are believed to beobvious. Not only is it possible to completely out off the dischargewhen the liquid level in the receiver reaches a point at which air wouldbe admitted to the pump, as by cessation of flow into the receiver, butshould there be a flow into the receiver less than that normallyprovided for, the discharge from the centrifugal pump will automaticallybe throttled to accord with such inflow to the receiver.

At no time will the centrifugal pump become air bound, nor will itsefficiency even be impaired as by the entrainment of some air withliquid to the eye of the impeller or other inlet to the pump.

In addition to maintenance of maximum efficiency in the pump, there willbe no tendency towards surging caused by the pump losing its supply ofliquid and thereafter having to pick up a fresh supply, since the pumpitself will in effect be submerged, at least insofar as the impeller eyeor the pump inlet are concerned, thus providing for uniform pumpingaction.

Certainly the deleterious results caused by pumping of air through thedischarge of the pump, to other parts of a system to which the apparatusmay be applied are completely avoided.

It will also be understood that the particular types of pilot valve,discharge control valve, controls for the pilot valve, and the like, areincluded as illustrative and not as limiting, except as hereinafterclaimed, as many variations will ocour to those skilled in the art.

While a centrifugal pump has been described herein as the type of pumpto which the control arrangement of the invention is applied, this ofcourse is also to be regarded as illustrative rather than limiting, acentrifugal pump of the type having a central eye or inlet, having beenpicked as that type of pump most susceptible to impairment inefl'iciency upon the introduction of air into its supply. It is obvious,however, that the control arrangement may be applied to any type ofliquid pump, not only to maintain efficient operation in the pump, butto prevent the transmission of air or gas beyond the pump where such airor gas might impair other portions of a system.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent of the United States is:

1. In pump controlling mechanism including a pump having a source ofliquid supply and a liquid discharge, comprising means to throttle thedischarge of the pump in accordance with the level of liquid at thesource of supply, the improvement which comprises liquid levelcontrolled means associated with the source of supply and operativelyconnected to said throttling means for efiecting the throttling action,said controlled means being constructed and arranged to utilize liquidby-passed from the discharge of the pump to its own suction to effectthe control of .the throttling means.

2. In pump controlling mechanism of the type including a pump having asource of liquid supply and a liquid discharge, and means to throttlethe discharge of the pump in accordance with the level of liquid at thesource of supply, the improvement which comprises means to utilize arecirculated portion of the liquid pumped to actuate the throttle meansby controlling the flow of liquid recirculated by liquid level means-atthe source of supply.

3. In pumping mechanism of the type having a pump, a source of liquidsupply, and means for admitting liquid from the said source to the pump,discharge means for the pump including a pressure controlled throttlevalve, the improvement which comprises a controlled by-pass connectingthe pressure control chamber of the throttle valve to said dischargemeans and to said source of liquid supply and liquid level controlledmeans associated with the source of liquid supply and controlling theflow of pumped liquid through said by-pass to cause variation in theunbalance of the pump differential pressure on the pressure controlledthrottle valve to control the discharge means in accordance withvariations in the level of the liquid in the source of supply.

4. In pumping mechanism of the type having a pump, a source of liquidsupply, and means for admitting liquid from the said source to the pump,discharge means for the pump including a pressure controlled throttlevalve, the improvement which comprises a controlled by-pass connectingthe pressure chamber of the throttle valve to said discharge means andto said source of liquid supply and liquid level controlled meansassociated with the source of liquid supply and controlling the flow ofpumped liquid through said by-pass to cause variation in the unbalanceof the pump differential pressure on the pressure controlled throttlevalve to cause said throttle valve to close when the level of the liquidin the source of supply descends to a predetermined elevation.

5. In pumping mechanism of the type having a. pump, a source of liquidsupply, and means for admitting liquid from the said source to the pump,discharge means for the pump including a pressure controlled throttlevalve, the improvement which comprises a liquid by-pass line connectingthe pressure control chamber of the throttle valve to said dischargemeans through a restriction and to said source of supply through a valvecontrolling flow of liquid therethrough but normally closing saidby-pass, and liquid level controlled means associated with the source ofliquid supply and connected to said valve for opening the latter andcause the resulting unbalanced pump differential pressure to close thethrottle means when the liquid level at said source descends to apredetermined elevation.

6. In a pump mechanism of the type having a pump, a source of liquidsupply, means for admitting liquid from said source to the pump,discharge means for the pump, including throttle means, said throttlemeans including a movable partition separating the pump discharge meansfrom a liquid control by-pass line connected to the discharge meansthrough a restricted orifice and connected to the source of liquidsupply through liquid level controlled means associated with the sourceof liquid supply, said liquid level controlled means causing theapplication of the pump diflerential pressure to the movable partitionto close the throttle means when the level of the liquid in the sourceor supply descends to a predetermined elevation.

7. In pumping mechanism of the type having a pump, a source of liquidsupply, and means for admitting liquid from the said source to the pump,discharge means for the pump including a pressure controlled throttlevalve, the improvement which comprises a liquid by-pass line connectingthe pressure control chamber of the throttle valve to said dischargemeans through a restriction and to said source of supply through a valvecontrolling the flow of liquid therethrough, electrically operated meansfor controlling the valve and liquid level controlled means to causeopening of said valve and thus to apply the resulting unbalanced pumpdillferential pressure to close the throttle means when the liquid levelat said source descends to a predetermined elevation.

HAROLD E. ADAMS.

